The present invention relates to the application of a solvent for a plastic label material to the surface of a series of plastic labels that are transported on a rotary drum for subsequent application of the individual label to a container.
It has been known to apply labels to containers by interposing a glue between the label and the container and rolling the label over the container to provide a full wrap-around label on the container. When dealing with plastic labels, it has been suggested that hot-melt adhesives or quick drying adhesives be used since, in order to label containers at a fairly rapid rate, it is necessary to get the adhesive transferred to the leading edge of the label and then bring the container into contact with the adhesive. The adhesive must be sufficiently tacky to assure adhesion of the label to the container during the subsequent rolling of the container along the label carrying drum and then the subsequent overlapping of the trailing end of the label over the leading edge with an interposed adhesive. In the event the label, so applied, is to be heat shrunk about the container, it is essential that the adhesion of the overlap or seam of the sleeve label be sufficient to resist separation under the shrinkage temperature and the tension from the circumferential shrinkage. U.S. Pat. No. 4,323,416 discloses, for example, an apparatus for gluing a label to a container by adhering the label to the container and subsequently wrapping the label about the container by rolling it along a fixed surface with the overlapping ends being glued together. Hot melt adhesives have been used in these circumstances but they are considered messy and expensive, since heat is required to maintain the adhesive at a useable temperature.
A more recent development disclosed in U.S. patent application Ser. No. 555,758, filed Nov. 28, 1983 now U.S. Pat. No. 4,574,020, assigned to the assignee of the present invention, describes apparatus for applying plastic labels to containers, such as plastic bottles, by using a solvent for the plastic of the label as the system for adhering the label to the container and also for making an overlap seam by using a solvent applied to the trailing edge of a label that is rolled completely about the container and overlaps the leading edge of the label.
The disclosure of this U.S. patent application Ser. No. 555,758 further describes the application of the solvent to the label by utilizing an applicator roll having a gravure pattern thereon corresponding to the distinct solvent patterns to be applied to the label at the leading and trailing edges of the label. The applicator roll is in the form of a cylinder that is mounted for rotation about a vertical axis. The roll has a vertical, solvent fountain in contact with its surface and in operation the gravure pattern on the surface of the roll will pick up the solvent in the pattern with the pattern position and roll diameter being related to the label length. The leading and trailing edges of a label carried on a transfer drum, which is moved in synchronism with the gravure roll and in general in contact therewith, will have solvent transferred thereto. The fountain has its open vertical face in contact with the applicator roll during its rotation and the majority of the solvent is intended to be in the gravure pattern with only an extremely thin film incidentally covering the rest of the roll. This incidental, thin film will normally evaporate during the operation of the system between contact with the fountain.